Why does my rigid body simulation glitch out?
Change the "Shape" (Under Rigidbody Collisions) from "Convex Hull" to "Mesh".

What's happening is that when you use Convex Hull, the simulation can only see a "shrinkwrapped" version of the shape. That is, it won't see the holes, and will therefore think that all the rings have ended up penetrating each other. To resolve this, it will apply a large-ish force to each object to force them apart, resulting in the explosion you see.